The present invention relates to a laser printer, and particularly to a compositive functional laser printer which is made to read a manuscript or to form a picture on a photo-sensitive drum by scanning laser beam by using a hologram disk.
A conventional laser printer is constituted with a laser beam to be outputted from the laser beam scanning optical unit in response to the contents desired to print, and a printing unit for printing by means of forming the picture on a photo-sensitive drum in accordance with the laser beam applied from said laser beam scanning optical unit.
Such a conventional laser printer will be explained by illustrating a typical exemplary form in FIGS. 1 and 2.
In the drawings, reference numeral 1 represents a laser beam scanning optical unit, 10 represents a printing unit, and 24 represents a computer, wherein said laser beam scanning optical unit 1 is constituted with a laser beam generator 2 for generating the laser beam, a collimator 3 for changing the laser beam into a parallel light, a cylindrical lens 4 for converging the parallel light passed through said collimator 3 to a rotary polyhedric mirror 5, compensation lenses 7 and 8 for compensating to make the laser beam reflected at said rotary polyhedric mirror 5 to be focused in correct picture on the photo-sensitive drum 11, and a reflective mirror 9 for deflecting the laser beam passed through said compensation lenses 7 and 8 on to the photo-sensitive drum 11.
And, said rotary polyhedric mirror 5 is rotated by a driving force of a driving motor 6, and said compensation lenses 7 and 8 have at least one toric surface.
The printing unit 10 comprises a photo-sensitive drum 11 on which the laser beam applied from said laser beam scanning optical unit 1 is focused, an electrifier 12, a developer 13, a transfer printer 14, a separator 15, an electricity remover 16, a fixing heater 17, and a cleaner arranged around the photo-sensitive drum 11 as well as a paper feeding, conveying and discharging means, the paper feeding, conveying and discharging means includes a cassette 19, paper feeding rollers 20, paper discharging rollers 21 and a paper discharging tray 22.
In the drawings, reference numeral 1' represents a casing of the laser beam scanning optical unit 1, and 23 represents a paper conveying guide.
According to the conventional laser printer as described above, a laser generator 2 emits a laser beam while it is turned to ON/OFF in response to the picture signal received from a computer 24, and the emitted laser beam is converted into a parallel light by the collimator 3 and converged on the mirror surface of the rotary polyhedric mirror 5 by the cylindrical lens 4.
And, the laser beam 1 converged to said rotary polyhedric mirror 5 is reflected at various angles as said rotary polyhedric mirror 5 is rotated by the driving force of the driving motor 6 and passing through the compensation lenses 7 and 8 and then scanned in the direction of arrow in FIG. 2, and this laser beam is deflected by the reflective mirror 9 whereby being converged on the photo-sensitive drum 11.
Wherein the compensation lenses 7 and 8 compensate the focal locus from a curved line to a straight line when the laser beam is converged and scanned on the photo-sensitive drum 11 and also compensate the laser beam being moved slightly perpendicular to the scanning plane due to an inclination of the mirror surface of the rotary polyhedric mirror 5 or a vibration of the mirror surface when the rotary polyhedric mirror 5 turns.
After the laser beam is focused on the photo-sensitive drum 11, printing is executed by the well known general printing process.
According to the conventional laser printer described above, since the toric lens and the cylindrical lens used in the laser beam scanning optical unit are difficult in working process, it has been a factor for increasing the cost of unit, and since the rotary polyhedric mirror is not only disadvantageous for mass production but also high in cost, the cost of unit has been further raised and productivity has been reduced. Moreover, according to such a conventional laser printer, since the laser beam scanning optical unit has a simple function of forming a picture on the photo-sensitive drum, it has been impossible to be used for use of other than a printer.